View Full Version : Apple II Repair & Restoration

Great Hierophant
May 25th, 2008, 07:00 AM
The Apple II/II+ may be about the most durable microcomputers ever made. If a hardware component breaks, most of the time it is simply a matter of replacing a socketed standard LS chip. The ROM chips may not be standard, but you can convert them. RAM is easy to obtain. Millions of 6502s were made, finding a replacement will not be difficult. None of the basic Apple expansion boards had difficult to locate chips. If you cannot find a replacement Apple speaker, use a PC one (or output it through a Mockingboard as I do.)

Now, when it comes to the Keyboard, there is another problem. 52 Keys = 52 possible errors. Replacement keyboards must come from old Apple II systems, which does not help the problem. The Keyboard encoder may have been standard back in the day, but no longer. Is there an economical solution?

May 25th, 2008, 07:34 AM

Ahh, the parallel ASCII keyboard question. This has plagued me many times -- vintage computers are notorious for it. Finding parallel ASCII keyboards is no small challenge either especially ones that match the original computer.

My VG and other machines use parallel ASCII keyboards. What I did is to use a PIC to make a serial to parallel converter and reused a scrap Kaypro II keyboard (300 bps serial link).

My PIC serial to parallel converter is not quite done yet but it works well enough. The code needs some serious clean up as it is primarily demonstration of proof of concept not really a final product.

I think what we really need is a circuit that can take cheap AT or PS2 keyboards and convert those to parallel ASCII. Vince Briel made something like it on his website. I have heard but not seen there are PIC codes available to convert AT/PS2 key scan codes to parallel ASCII.

Making the PCB would be simple enough in KiCad but I am in the middle of enough things I don't really want to take this on right now. Thoughts?

Thanks and good luck in your search!

Andrew Lynch

May 26th, 2008, 05:12 PM
I find that the sockets are the weak point of the motherboard design. Most all of the old circuit boards I have recently used, have had issues at one time or another with flakey connections between sockets and ICs. Somewhere on one of those vintage computer history sites, is a comment by an early employee indicating that this was a problem from day one.

Here is a simple design that uses a PIC in order to interface a PS/2 keyboard to an Apple Keyboard port.

Mike Willegal

May 26th, 2008, 06:51 PM
The keys on the Apple ][+ that I have are just standard Alps two leg keys.

When I got it, the right shift key shaft was broken so, I just pulled a key out of a Tandy Model I keyboard I had laying around, extracted the broken one and popped in the new one.

Worked fine.

I don't know about the encoder chip, but, I still have some KB3600s for the Apple ][ and a Programmer's Aid #1 (341-0016) for the Apple ][ as well